it makes it less likely that your skis will catch smearing around on jumps. It also makes it fun to press and butter.
A rocker like the alpha 1 seems strange to me. I have a pretty long, shallow rocker on my park skis. At the beginning of the year, I learned how to hold a true nose press (claim!) on small boxes. A better skier could make it real sick on longer higher boxes or rails. Since it's shallow, I don't notice making any difference popping off jumps or onto rails.
it does, however, mean that you have to land a little more centered. Your skis will wash out more than a flatter ski if you land strange, but it's really not much of a problem.